Different types of lamps are known for use in an automotive headlight. The present invention relates to incandescent lamps, i. e. lamps where light is generated from one or more filaments arranged within a transparent lamp vessel.
Known lamp types comprise lamps where a shield is arranged adjacent to a filament such that light emitted from the filament is partly blocked, and such that an angular shielded region is obtained into which no direct light from the filament is emitted. The obtained illumination beam of light includes a bright/dark cutoff caused by the shield, which may be used to form in a reflector an illumination beam pattern with a bright/dark cutoff, which may be used e. g. for low beam illumination. An example of a double filament lamp where a shield is provided adjacent to one of the filaments is a H4 lamp. Other lamps, in particular single filament lamps such as e. g. a H7 lamp do not provide a shield.
Automotive regulations cover geometrical parameters of an automotive lamp, such as the position and size of filaments as well as functional parameters, such as the color of the light emitted. Such regulations provide that the illumination beam of light emitted from the lamp to serve the purpose of illuminating the road in front of the motor vehicle is required to have a white color, i. e. the color of the emitted light must be within a specified white field of color coordinates.
DE 10 2010 002 084 A1 describes a halogen incandescent lamp for a vehicle front reflector comprising, in one embodiment, a lamp vessel with two filaments, of which one serving for low beam lighting is arranged adjacent to a shield. The lamp vessel comprises an optical filter to obtain violet coloring of the light emitted. In different embodiments, a color filter may be applied to a single filament lamp without a shield, and the lamp vessel may be fully or partially covered by the color filter. The light emitted from the lamp is within the white field of the ECE regulations, but has a violet coloring, such that the vehicle may be recognized by the light color. In a specific embodiment, it is disclosed that part of the lamp vessel is not covered by a color filter, resulting in an uncolored central part of the light beam and a colored edge region of the light beam. Part of the light beam is therefore colored. The coloring of this part of the beam should also remain with the boundaries set by the regulations and therefore only a limited color change is possible.